Bottom Line:
Thermal stability and decomposition studies of the obtained two new γ-octamolybdates were performed using TG/DSC and XRPD methods.Both compounds decomposed with the formation of 4-methylpyridinium β-octamolybdate.The two compounds are pseudo-polymorphs, exhibiting both striking similarities as well as significant differences in their structures and properties.

Abstract: We synthesized two new γ-octamolybdates, and determined their crystal structures from single-crystal X-ray diffraction data. Orange-yellow tetrakis(4-methylpyridinium) bis(4-methylpyridine)-γ-octamolybdate 1 crystallizes in space group P21/c with a = 11.586(2) Å, b = 15.526(2) Å, c = 16.247(2) Å, β = 118.753(1)º, Z = 2. White tetrakis(4-methylpyridinium) bis(4-methylpyridine)-γ-octamolybdate hydrate 2 crystallizes in space group C2/c with a = 27.086(4) Å, b = 11.917(2) Å, c = 19.332(2) Å, β = 124.427(1)º, Z = 4. Results of crystal structure determinations are presented and discussed in this paper. Thermal stability and decomposition studies of the obtained two new γ-octamolybdates were performed using TG/DSC and XRPD methods. Both compounds decomposed with the formation of 4-methylpyridinium β-octamolybdate. The two compounds are pseudo-polymorphs, exhibiting both striking similarities as well as significant differences in their structures and properties.

Mentions:
So far, eight isomers of octamolybdates are known: α, β, γ, δ, ε, ζ, η, and θ. The best-known and also the most commonly occurring is the beta-isomer. Other isomers are much less likely to occur. Construction of the individual isomer is described in the scientific literature [3, 5]. The choice of reaction conditions has a major influence on the formation of a specific form. One such little-known isomer is the γ isomer, which Klemperer and Shum [1] proposed as an intermediate between the α- and β-isomers, to explain the inter-conversion of these forms. It consists of six MO6 octahedra and two MO5 square pyramid subunits [1, 3]. Moreover, in many cases of Mo atoms, occupying the centrt of MoO5 pyramids, organic ligands are coordinated, forming species with the formula Mo8O26(L2)2n − 4 (where L denotes ligands other than terminal oxygen, n charge of ligand L). Also of interest is an examination of the gamma isomers in terms of their high biological activity [6]. Figure 1 presents three octamolybdate isomers: α, β, and γ.Fig. 1

Mentions:
So far, eight isomers of octamolybdates are known: α, β, γ, δ, ε, ζ, η, and θ. The best-known and also the most commonly occurring is the beta-isomer. Other isomers are much less likely to occur. Construction of the individual isomer is described in the scientific literature [3, 5]. The choice of reaction conditions has a major influence on the formation of a specific form. One such little-known isomer is the γ isomer, which Klemperer and Shum [1] proposed as an intermediate between the α- and β-isomers, to explain the inter-conversion of these forms. It consists of six MO6 octahedra and two MO5 square pyramid subunits [1, 3]. Moreover, in many cases of Mo atoms, occupying the centrt of MoO5 pyramids, organic ligands are coordinated, forming species with the formula Mo8O26(L2)2n − 4 (where L denotes ligands other than terminal oxygen, n charge of ligand L). Also of interest is an examination of the gamma isomers in terms of their high biological activity [6]. Figure 1 presents three octamolybdate isomers: α, β, and γ.Fig. 1

Bottom Line:
Thermal stability and decomposition studies of the obtained two new γ-octamolybdates were performed using TG/DSC and XRPD methods.Both compounds decomposed with the formation of 4-methylpyridinium β-octamolybdate.The two compounds are pseudo-polymorphs, exhibiting both striking similarities as well as significant differences in their structures and properties.

Abstract: We synthesized two new γ-octamolybdates, and determined their crystal structures from single-crystal X-ray diffraction data. Orange-yellow tetrakis(4-methylpyridinium) bis(4-methylpyridine)-γ-octamolybdate 1 crystallizes in space group P21/c with a = 11.586(2) Å, b = 15.526(2) Å, c = 16.247(2) Å, β = 118.753(1)º, Z = 2. White tetrakis(4-methylpyridinium) bis(4-methylpyridine)-γ-octamolybdate hydrate 2 crystallizes in space group C2/c with a = 27.086(4) Å, b = 11.917(2) Å, c = 19.332(2) Å, β = 124.427(1)º, Z = 4. Results of crystal structure determinations are presented and discussed in this paper. Thermal stability and decomposition studies of the obtained two new γ-octamolybdates were performed using TG/DSC and XRPD methods. Both compounds decomposed with the formation of 4-methylpyridinium β-octamolybdate. The two compounds are pseudo-polymorphs, exhibiting both striking similarities as well as significant differences in their structures and properties.